Comparison of the membrane glycoproteins of control and malignant cells has revealed a difference in their bound carbohydrate groups. The difference which occurs in the sugar groups of over 80% of the glycoproteins in all the membrane systems of the cell is very widespread occurring in five species of cells in solid tumors and malignant cells in culture. The significance of this finding is unknown because aside from a few well known dramatic examples of involvement of bound sugars in specific function, the basic role of bound sugars is not really known. We have formulated an hypothesis which may answer the question why proteins bear carbohydrates. Experiments that may provide some answers to this question of protein bound carbohydrates are proposed. We also plan to complete comparative studies to determine the structure and the biosynthesis of protein-bound carbohydrates of control and transformed cells. We will continue studies determining the amino acids of specific glycoproteins that are glycosylated. Is the "wrong" amino acid glycosylated in the malignant cell?